Editor's Note — CNN Travel updates this article periodically. It was last updated in its entirety on June 15.
(CNN) — US passport holders have more international travel options now than at any point during the Covid-19 pandemic. Total US cases are nearing the 33.5 million mark since the pandemic started, but the rate of new cases has been slowing down recently. The United States is one of the world leaders in vaccination rates and has been leading among nations with a population over 100 million. But we're not out of the woods -- the US Centers for Disease Control and Prevention said June 15 that the Delta variant of the novel coronavirus, also known as B.1.617.2, is a "variant of concern." Still, more of Europe is opening up to US leisure travelers in time for summer -- especially the fully vaccinated. Travel heavyweights France and Spain are the latest to open their doors. The global situation is in flux, though. Even as some places reopen for the first time, others are closing back up. In the end, it's up to you to decide whether travel to international destinations is a good idea. The health risks are obvious if you're not fully vaccinated. Nations might change their rules at any time. You may have to adhere to strict curfews and mask mandates. Violations could involve big fines and even jail time. If you want expert input into your decision, the US State Department and the CDC provide Covid-19 risk assessments by country. Both agencies rate many of the countries open to US travelers at Level 4, the highest risk for Covid-19. Also, remember that all air passengers 2 and older must show proof of a negative Covid-19 test that's no more than three days old to enter the United States.
What follows is an alphabetical list of countries and territories where it's still possible for US passport holders to go for a vacation. Click the links we've provided for very important information on:
-- Presenting negative results from Covid-19 tests to enter (including time limits to take the test, types of tests allowed and additional tests upon arrival).
-- Quarantines (if any) and health screenings.
-- Possible exemptions from the rules for the fully vaccinated or people recovered from a recent case of Covid-19.
-- Health insurance requirements, curfews and lockdowns.
These are all things you need to research before you book your trip. People testing positive for Covid-19 upon arrival or while visiting can expect to go into quarantine. Rules for land entry may be different.
Blessed with a gorgeous Adriatic Sea coastline, this southeastern European country has no test requirements or quarantine. Details and updates: US Embassy.
US visitors will once again have access to the tropical waters of Anguilla.
Courtesy Belmond Cap Juluca
Antigua and Barbuda
Scroll down to the Dutch Caribbean entry below for information on Aruba and other islands in this group.
This populous South Asian nation offers beaches, interesting architecture and cultural experiences. Testing and quarantine requirements are in place. Details and updates: US Embassy.
Why do people come to Barbados? For starters, places such as Bottom Bay.
English is spoken in this Central American nation filled with wildlife spotting opportunities and stunning barrier reefs. Testing required; fully vaccinated exempt. No quarantine in place. Details and updates: US Embassy | Belize Tourism Board.
This landlocked South American country offers surreal landscapes from Andean to jungle. Testing and quarantine requirements in place. Details and updates: US Embassy.
Bosnia and Herzegovina
Bosnia and Herzegovina features cosmopolitan Sarajevo and gorgeous lakes. Testing required; quarantine is not. Details and updates: US Embassy | Bosnia Border Police
Botswana is renowned for its safari opportunities. Elephants are always a top sighting on any excursion.
This southern African nation is famed for its wildlife in the Okavango Delta and elsewhere. Testing and quarantine requirements are in place. Details and updates: US Embassy.
South America's largest country has the lure of Rio's party atmosphere and the Amazon River's mystique. It also has a very high daily number of Covid-19 cases. Testing required; quarantines are not. Details and updates: US Embassy | Health declaration.
British Virgin Islands
Historic towns and natural landscapes are Bulgaria's calling cards. Testing required; exemptions for fully vaccinated or recovered from Covid-19 infection. No quarantine. Details and updates: US Embassy.
Downtown Medellin is a great place to take a stroll and soak up urban Colombian atmosphere.
Côte d'Ivoire (Ivory Coast)
Côte d'Ivoire is a popular destination for people wanting to enjoy West African culture and food. Testing required; quarantine encouraged but not required. Details and updates: US Embassy | Travel declaration and fee.
Croatia, the jewel of the Adriatic, is once again open to US leisure travelers. Testing required to enter; exemptions for the fully vaccinated or recovered from Covid-19 infection. No standard quarantine in place. Details and updates: US Embassy | Croatia official entry form.
Both parts of this politically divided Mediterranean island are open to US tourists. The Republic of Cyprus and the northern third of the island administered by Turkish Cypriots (Turkish Republic of Northern Cyprus) each have their own rules of entry and testing. Details and updates: US Embassy in Nicosia | Visit Cyprus.
Copenhagen, the capital city, is both quaint and sophisticated at the same time.
Odd Andersen/AFP/Getty Images
Scroll down to the United Arab Emirates entry below.
Dutch Caribbean islands
Find out the important details on these various Dutch islands in the Caribbean -- renowned for their hospitality and ocean life -- by clicking on the links:
Saba (new): Known more for its rugged landscape and hiking than beaches, little Saba is open. Testing required. Quarantine in place; exemption for fully vaccinated. Details and updates: Saba Tourism | Saba EHAS application.
The animals of the Galapogos Islands, part of Ecuardor, fascinate scientists and tourists alike.
PABLO COZZAGLIO/AFP via Getty Images
This Andean country at the equator also owns the Galápagos Islands in the Pacific. Testing required; fully vaccinated exempted. Quarantine required in some circumstances. Details and updates: US Embassy.
The Nile River nation has been attracting people to see its wonders for many centuries. Testing required; quarantine is not. Details and updates: US Embassy.
Ethiopia has a unique and ancient culture and rugged, otherworldly landscapes. Testing and quarantine requirements are in place. Before you travel there, closely monitor news reports about violence in the northern Tigray region (video) on the border with Eritrea. Details and updates: US Embassy.
UPDATE: Georgia is a geographical and cultural crossroads at the Caucasus Mountains. Testing required unless you're fully vaccinated. No self-isolation for the unvaccinated under certain conditions. Details and updates: US Embassy | Georgian Ministry of Foreign Affairs.
This West African cultural jewel offers historical sites, delicious food and surfing. Testing required. No quarantine. Details and updates: US Embassy.
Beautiful houses grace the port of Gytheio on the Peloponnese.
Greece, with its many ancient ruins and islands, is now open to US travelers. Testing required; exception for the fully vaccinated. No quarantine. Details and updates: US Embassy | Passenger locator form.
This Central American country offers historical sites and stunning volcano landscapes. Testing required; exceptions for the fully vaccinated or those fully recovered from Covid-19. No quarantine. Details and updates: US Embassy | Online health pass.
UPDATE: Honduras has epic diving off Roatan Island and other locations. Testing required; fully vaccinated travelers are exempt. Conditional quarantine in some circumstances. Details and updates: US Embassy | Online precheck form.
Geysers, glaciers, hot springs and waterfalls await in Iceland. You must be fully vaccinated or have proof of recovery from Covid-19 to enter. Testing and quarantine requirements in place as well. Details and updates: US Embassy | Iceland travel registration.
Great Blasket Island is a hiker's paradise -- and the donkeys seem to like it, too.
Courtesy Tourism Ireland
NEW: From ancient Jerusalem to modern Tel Aviv, Israel now allows US tourists. Testing required. Quarantine in place for those not fully vaccinated or recovered from a case of Covid-19. You should keep a close watch on developments as you plan your trip regarding the recent conflict between Israel and Gaza. Details and updates: US Embassy | Israel Ministry of Health.
A visit to Jordan's ancient city of Petra is a travel highlight not only of the Arab nation but of the entire world.
KHALIL MAZRAAWI/afp/AFP via Getty Images
Home to the amazing ruins of Petra, Dead Sea coastline and the dazzling landscape of the Wadi Rum, Jordan is open to US vacationers. Testing required; quarantine is not. Details and updates: US Embassy.
Kenya is the definitive African safari destination, but Nairobi's urban beat attracts tourists too. Testing required; no quarantine. Details and updates: US Embassy | Trusted Travel initiative.
The land border between the US and Mexico remains closed through at least June 21, but US travelers can still fly there. No testing or quarantine requirements are in place. The US State Department lists numerous states to avoid because of crime. Details and updates: US Embassy.
This Balkan nation is allowing US travelers. Testing under most circumstances required; exceptions for the fully vaccinated or the naturally immune because of previous Covid-19 illness. Details and updates: US Embassy | Institute of Public Health of Montenegro.
UPDATE: Starting June 15, this North African favorite is open leisure travelers from the United States without special invitations. Testing required, but no quarantines in place. Details and updates: US Embassy | Visit Morocco.
UPDATE: US citizens can visit this southern African desert nation that appeals to adventure travelers. Testing required; quarantine is not. Details and updates: US Embassy.
US travelers can visit the landlocked Himalayan nation. Testing and quarantine requirements in place, regardless of vaccination status. Details and updates: US Embassy.
The Cathedral of Granada is a popular site.
Home to historical sites such as Granada and tropical beaches, Nicaragua is open. Testing required; quarantines are not. Details and updates: US Embassy | Avianca Airlines.
North Macedonia has a part Balkan, part Mediterranean feel and its natural wonders are relatively unknown. No testing or quarantine required. Details and updates: US Embassy | TAV Macedonia.
US travelers now have a travel window to get their Lisbon fix.
Courtesy Jessica Yubas
NEW: Portugal is open to US citizens from June 15 to 27. The measure will be reviewed every two weeks and unless renewed expires midnight on June 27. Testing is required; quarantine is a possibility. Details and updates: US Embassy.
NEW: Romania offers mystique, wooded and mountainous landscapes and lots of history. No testing required. Quarantine in place with exceptions for fully vaccinated and those recovered from Covid-19. Details and updates: US Embassy | Romanian Embassy.
Rwanda's green hills and mountains are home to rare gorillas. Testing and quarantine requirements are in place. Details and updates: US Embassy | Visit Rwanda.
Senegal, known for its West African beaches and music, welcomes US tourists. Testing is required; no quarantine in place. Details and updates: US Embassy.
Serbia features noteworthy architecture. City Hall is in the city of Subotica in the far north of the country, near the border with Hungary.
Serbia is steeped in historical sites and dramatic Eastern European scenery. Testing is required but quarantines are not. Details and updates: US Embassy.
With superb national parks, wineries and the allure of Cape Town, one of the most popular destinations in Africa is open. Testing is required; quarantine is not. Be aware some nations aren't allowing entry to tourists who have recently been to South Africa. Details and updates: US Embassy.
From busy Seoul to relaxing Jeju Island, South Korea is open. Testing and quarantine requirements are in place. Details and updates: US Embassy | Self-diagnosis app
NEW: After an extended closure, this French island is allowing fully vaccinated travelers from the United States. Testing required. Details and updates: St. Barts entry protocols
St. Kitts and Nevis
Home of the steep and towering Pitons, waterfalls and volcanic beaches, the independent Caribbean nation of St. Lucia is open. Testing and quarantine requirements are in place. Details and updates: US Embassy | St. Lucia travel website.
St. Vincent and the Grenadines
Kilimanjaro's glaciers could become a thing of the past as average global temperatures rise.
Sergey Pesterev/Flickr Open/Getty Images/Flickr Open
A favorite for big-game safaris, Indian Ocean beaches and Mount Kilimanjaro, Tanzania is open. Testing required; quarantine is not. Details and updates: US Embassy | Health surveillance form.
US passport holders can again visit this fascinating Southeast Asian destination famed for its beautiful beaches and spicy cuisine. Testing and quarantine requirements are in place. Details and updates: US Embassy | Royal Thai Embassy | Certificate of entry.
Tunisia offers ancient ruins, desert scenery and sunny Mediterranean beaches. Testing and quarantine requirements in place. Fully vaccinated visitors are exempt from both. Details and updates: US Embassy | Online questionnaire.
From cosmopolitan Istanbul to rural coastal escapes, Turkey is open. Testing is required; quarantine is not. Details and updates: US Embassy | Form for entry.
Turks and Caicos
Visitors with a respectful approach and careful eye might see a giant gorilla munching shoots and leaves.
This lush nation in Central Africa offers gorilla trekking, Nile River rafting and beautiful lakes. Testing required; quarantine is not. Details and updates: US Embassy.
United Arab Emirates
The UAE, with its glittering towers and luxury resorts, has emerged as a major world destination in the 21st century. Testing required. Quarantine protocols depend on the emirate. Details and updates: US Embassy.
Leisure travel to the UK is highly discouraged but not banned. Testing and quarantine requirements are in place. Rules may vary between England, Scotland, Wales and Northern Ireland. Details and updates: US Embassy | UK government | Declaration form.
Known for Victoria Falls and wildlife, Zambia is allowing visitors. Testing and quarantine requirements are in place. Details and updates: US Embassy.
Recently removed from the open list
The following countries had been allowing US citizens to enter but have closed again or were removed by CNN Travel for other reasons:
-- Cambodia: The US Embassy reports the Southeast Asian nation has stopped issuing tourist visas; you can still apply for business-linked visas.
-- Chile: It has closed its borders to almost all tourists through June 30.
-- Sri Lanka: No international flights allowed until June 1.
This is a curated list and not a full listing. CNN Travel has omitted certain open countries if they had very limited numbers of US travelers before the pandemic; have ongoing or recent armed conflicts, terrorism or rampant crime and unrest; or have entry requirements so extensive and complicated that they put the country out of reach of almost all US citizens. However, you can click here to check for the status and entry requirements of any country or territory in the world you wish to visit.